[PATCH for 3.12-rcX] mutex: Avoid gcc version dependent __builtin_constant_p() usage.

From: Tetsuo Handa
Date: Thu Oct 03 2013 - 10:03:14 EST

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Peter Zijlstra wrote:
> On Mon, Sep 09, 2013 at 08:56:53PM +0900, Tetsuo Handa wrote:
> > From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
> > Date: Mon, 9 Sep 2013 20:48:13 +0900
> > Subject: [PATCH] mutex: Avoid gcc version dependent __builtin_constant_p() usage.
> >
> > Commit 040a0a37 "mutex: Add support for wound/wait style locks" used
> > "!__builtin_constant_p(p == NULL)" but gcc 3.x cannot handle such expression
> > correctly, leading to boot failure when built with CONFIG_DEBUG_MUTEXES=y.
> >
> > Fix it by explicitly passing a bool which tells whether p != NULL or not.
> >
> > Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
> > Cc: <stable@xxxxxxxxxx> [3.11+]
> > ---
> > kernel/mutex.c | 32 ++++++++++++++++----------------
> > 1 files changed, 16 insertions(+), 16 deletions(-)
> >
> > diff --git a/kernel/mutex.c b/kernel/mutex.c
> > index a52ee7bb..a2b80f1 100644
> > --- a/kernel/mutex.c
> > +++ b/kernel/mutex.c
> > @@ -408,7 +408,7 @@ ww_mutex_set_context_fastpath(struct ww_mutex *lock,
> > static __always_inline int __sched
> > __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
> > struct lockdep_map *nest_lock, unsigned long ip,
> > - struct ww_acquire_ctx *ww_ctx)
> > + struct ww_acquire_ctx *ww_ctx, const bool use_ww_ctx)
> > {
> > struct task_struct *task = current;
> > struct mutex_waiter waiter;
> > @@ -448,7 +448,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
> > struct task_struct *owner;
> > struct mspin_node node;
> >
> > - if (!__builtin_constant_p(ww_ctx == NULL) && ww_ctx->acquired > 0) {
> > + if (use_ww_ctx && ww_ctx->acquired > 0) {
> > struct ww_mutex *ww;
> >
> > ww = container_of(lock, struct ww_mutex, base);
> > @@ -478,7 +478,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
> > if ((atomic_read(&lock->count) == 1) &&
> > (atomic_cmpxchg(&lock->count, 1, 0) == 1)) {
> > lock_acquired(&lock->dep_map, ip);
> > - if (!__builtin_constant_p(ww_ctx == NULL)) {
> > + if (use_ww_ctx) {
> > struct ww_mutex *ww;
> > ww = container_of(lock, struct ww_mutex, base);
> >
> > @@ -548,7 +548,7 @@ slowpath:
> > goto err;
> > }
> >
> > - if (!__builtin_constant_p(ww_ctx == NULL) && ww_ctx->acquired > 0) {
> > + if (use_ww_ctx && ww_ctx->acquired > 0) {
> > ret = __mutex_lock_check_stamp(lock, ww_ctx);
> > if (ret)
> > goto err;
> > @@ -568,7 +568,7 @@ done:
> > mutex_remove_waiter(lock, &waiter, current_thread_info());
> > mutex_set_owner(lock);
> >
> > - if (!__builtin_constant_p(ww_ctx == NULL)) {
> > + if (use_ww_ctx) {
> > struct ww_mutex *ww = container_of(lock,
> > struct ww_mutex,
> > base);
> > @@ -618,7 +618,7 @@ mutex_lock_nested(struct mutex *lock, unsigned int subclass)
> > {
> > might_sleep();
> > __mutex_lock_common(lock, TASK_UNINTERRUPTIBLE,
> > - subclass, NULL, _RET_IP_, NULL);
> > + subclass, NULL, _RET_IP_, NULL, 0);
> > }
> >
> > EXPORT_SYMBOL_GPL(mutex_lock_nested);
>
> This is a sad patch, but provided it actually generates similar code I
> suppose its the best we can do bar whole sale deprecating gcc-3.
>

Can the patch below go to 3.12-rcX (and the patch above to 3.11-stable which
does the same thing)?

Regards.
----------
>From a1b01c858143c2c2c92b17e7df096042bfe0df6b Mon Sep 17 00:00:00 2001
From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Date: Tue, 24 Sep 2013 23:44:17 +0900
Subject: [PATCH] mutex: Avoid gcc version dependent __builtin_constant_p() usage.

Commit 040a0a37 "mutex: Add support for wound/wait style locks" used
"!__builtin_constant_p(p == NULL)" but gcc 3.x cannot handle such expression
correctly, leading to boot failure when built with CONFIG_DEBUG_MUTEXES=y.

Fix it by explicitly passing a bool which tells whether p != NULL or not.

Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
---
kernel/mutex.c | 32 ++++++++++++++++----------------
1 files changed, 16 insertions(+), 16 deletions(-)

diff --git a/kernel/mutex.c b/kernel/mutex.c
index 6d647ae..d24105b 100644
--- a/kernel/mutex.c
+++ b/kernel/mutex.c
@@ -410,7 +410,7 @@ ww_mutex_set_context_fastpath(struct ww_mutex *lock,
static __always_inline int __sched
__mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
struct lockdep_map *nest_lock, unsigned long ip,
- struct ww_acquire_ctx *ww_ctx)
+ struct ww_acquire_ctx *ww_ctx, const bool use_ww_ctx)
{
struct task_struct *task = current;
struct mutex_waiter waiter;
@@ -450,7 +450,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
struct task_struct *owner;
struct mspin_node node;

- if (!__builtin_constant_p(ww_ctx == NULL) && ww_ctx->acquired > 0) {
+ if (use_ww_ctx && ww_ctx->acquired > 0) {
struct ww_mutex *ww;

ww = container_of(lock, struct ww_mutex, base);
@@ -480,7 +480,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
if ((atomic_read(&lock->count) == 1) &&
(atomic_cmpxchg(&lock->count, 1, 0) == 1)) {
lock_acquired(&lock->dep_map, ip);
- if (!__builtin_constant_p(ww_ctx == NULL)) {
+ if (use_ww_ctx) {
struct ww_mutex *ww;
ww = container_of(lock, struct ww_mutex, base);

@@ -551,7 +551,7 @@ slowpath:
goto err;
}

- if (!__builtin_constant_p(ww_ctx == NULL) && ww_ctx->acquired > 0) {
+ if (use_ww_ctx && ww_ctx->acquired > 0) {
ret = __mutex_lock_check_stamp(lock, ww_ctx);
if (ret)
goto err;
@@ -575,7 +575,7 @@ skip_wait:
lock_acquired(&lock->dep_map, ip);
mutex_set_owner(lock);

- if (!__builtin_constant_p(ww_ctx == NULL)) {
+ if (use_ww_ctx) {
struct ww_mutex *ww = container_of(lock, struct ww_mutex, base);
struct mutex_waiter *cur;

@@ -615,7 +615,7 @@ mutex_lock_nested(struct mutex *lock, unsigned int subclass)
{
might_sleep();
__mutex_lock_common(lock, TASK_UNINTERRUPTIBLE,
- subclass, NULL, _RET_IP_, NULL);
+ subclass, NULL, _RET_IP_, NULL, 0);
}

EXPORT_SYMBOL_GPL(mutex_lock_nested);
@@ -625,7 +625,7 @@ _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest)
{
might_sleep();
__mutex_lock_common(lock, TASK_UNINTERRUPTIBLE,
- 0, nest, _RET_IP_, NULL);
+ 0, nest, _RET_IP_, NULL, 0);
}

EXPORT_SYMBOL_GPL(_mutex_lock_nest_lock);
@@ -635,7 +635,7 @@ mutex_lock_killable_nested(struct mutex *lock, unsigned int subclass)
{
might_sleep();
return __mutex_lock_common(lock, TASK_KILLABLE,
- subclass, NULL, _RET_IP_, NULL);
+ subclass, NULL, _RET_IP_, NULL, 0);
}
EXPORT_SYMBOL_GPL(mutex_lock_killable_nested);

@@ -644,7 +644,7 @@ mutex_lock_interruptible_nested(struct mutex *lock, unsigned int subclass)
{
might_sleep();
return __mutex_lock_common(lock, TASK_INTERRUPTIBLE,
- subclass, NULL, _RET_IP_, NULL);
+ subclass, NULL, _RET_IP_, NULL, 0);
}

EXPORT_SYMBOL_GPL(mutex_lock_interruptible_nested);
@@ -682,7 +682,7 @@ __ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)

might_sleep();
ret = __mutex_lock_common(&lock->base, TASK_UNINTERRUPTIBLE,
- 0, &ctx->dep_map, _RET_IP_, ctx);
+ 0, &ctx->dep_map, _RET_IP_, ctx, 1);
if (!ret && ctx->acquired > 1)
return ww_mutex_deadlock_injection(lock, ctx);

@@ -697,7 +697,7 @@ __ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)

might_sleep();
ret = __mutex_lock_common(&lock->base, TASK_INTERRUPTIBLE,
- 0, &ctx->dep_map, _RET_IP_, ctx);
+ 0, &ctx->dep_map, _RET_IP_, ctx, 1);

if (!ret && ctx->acquired > 1)
return ww_mutex_deadlock_injection(lock, ctx);
@@ -809,28 +809,28 @@ __mutex_lock_slowpath(atomic_t *lock_count)
struct mutex *lock = container_of(lock_count, struct mutex, count);

__mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, 0,
- NULL, _RET_IP_, NULL);
+ NULL, _RET_IP_, NULL, 0);
}

static noinline int __sched
__mutex_lock_killable_slowpath(struct mutex *lock)
{
return __mutex_lock_common(lock, TASK_KILLABLE, 0,
- NULL, _RET_IP_, NULL);
+ NULL, _RET_IP_, NULL, 0);
}

static noinline int __sched
__mutex_lock_interruptible_slowpath(struct mutex *lock)
{
return __mutex_lock_common(lock, TASK_INTERRUPTIBLE, 0,
- NULL, _RET_IP_, NULL);
+ NULL, _RET_IP_, NULL, 0);
}

static noinline int __sched
__ww_mutex_lock_slowpath(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
{
return __mutex_lock_common(&lock->base, TASK_UNINTERRUPTIBLE, 0,
- NULL, _RET_IP_, ctx);
+ NULL, _RET_IP_, ctx, 1);
}

static noinline int __sched
@@ -838,7 +838,7 @@ __ww_mutex_lock_interruptible_slowpath(struct ww_mutex *lock,
struct ww_acquire_ctx *ctx)
{
return __mutex_lock_common(&lock->base, TASK_INTERRUPTIBLE, 0,
- NULL, _RET_IP_, ctx);
+ NULL, _RET_IP_, ctx, 1);
}

#endif
--
1.7.1
--
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